An investigation of the mechanism of visual excitation in vertebrates. BIBLIOGRAPHIC REFERENCES: Weinstein, J. N., Yoshikami, S., Henkart, P., Blumenthal, R. and Hagins, W. A.: Liposome-Cell Interaction: Transfer and Intracellular Release of a Trapped Fluorescent Marker, Science, 195, 489-492 (1977). Hagins, W. A. and Yoshikami, S.: Intracellular Transmission of Visual Excitation in Vertebrate Retinal Photoreceptors: Electrical Effects of Chelating Agents Introduced into Rods by Vesicle Fusion, Rank Prize Fund Symposium on Photoreception, London, 1976, H. B. Barlow and P. Fatt, eds. New York, Academic, in press.